Pascal Costanza schrieb: > Static type systems potentially change the semantics of a > language in ways that cannot be captured by dynamically typed languages > anymore, and vice versa.
Very true. I also suspect that's also why adding type inference to a dynamically-typed language doesn't give you all the benefits of static typing: the added-on type system is (usually) too weak to express really interesting guarantees, usually because the language's semantics isn't tailored towards making the inference steps easy enough. Conversely, I suspect that adding dynamic typing to statically-typed languages tends to miss the most interesting applications, mostly because all the features that can "simply be done" in a dynamically-typed language have to be retrofitted to the statically-typed language on a case-by-case basis. In both cases, the language designers often don't know the facilities of the opposed camp well enough to really assess the trade-offs they are doing. > There is, of course, room for research on performing static type checks > in a running system, for example immediately after or before a software > update is applied, or maybe even on separate type checking on software > increments such that guarantees for their composition can be derived. > However, I am not aware of a lot of work in that area, maybe because the > static typing community is too focused on compile-time issues. I think it's mostly because it's intimidating. The core semantics of an ideal language fits on a single sheet of paper, to facilitate proofs of language properties. Type checking dynamically-loaded code probably wouldn't fit on that sheet of paper. (The non-core semantics is then usually a set of transformation rules that map the constructs that the programmer sees to constructs of the core language.) Regards, Jo -- http://mail.python.org/mailman/listinfo/python-list
